Can you please point me to an article where Trump called the leaders of all our allies to create a coalition? And also which collective sanctions were created?

It's complicated to get buy-in on actual sanctions within the anglosphere and Europe, but it's not as though the U.S. is not pushing for them. [0]

[0]: https://www.ft.com/content/fcaf0a57-ac0f-4695-af0f-82a44e6ae...

The UK and Australia are willing to flap their mouths a bit [1] over it at least, and the UK is much closer to actual sanctions (Australia has, for the time being, not terminated their special trade arrangements with Hong Kong).

[1]: https://americanmilitarynews.com/2020/05/us-uk-canada-and-au...

Ultimately only the U.S. has taken any leadership on this matter, even if I think it will be inadequate. There is more to be done; but with the U.S. Presidential election looming, one thing that would steel the resolve and buff the resources of PRC assets in American politics would be a major announcement.

Nothing is as simple as the free world bullying the nominally-free world to condemn the only major state in the world conducting a holocaust; because apparently those "allies" don't give a toss.